1. Field of the Invention
The present invention relates to a pipe expanding tool for expanding an end of a tube, for example, a tube for introduction and discharge of a fluid.
2. Description of the Related Art
Heretofore, a pipe expanding tool has been known for expanding an end of a tube made from a synthetic resin, the pipe expanding tool serving as a mounting jig, which is used when the tube is connected to a pipe joint.
For example, as disclosed in U.S. Pat. No. 5,382,151, such a pipe expanding tool 1 is constituted from a pair of levers 3, 4, which are connected rotatably via a rotary shaft 2. A pair of grips 5, 6 is provided on one of the ends of the pair of levers 3, 4, whereas a pair of plate-shaped jaws 7, 8 is provided on the other ends thereof. A pair of semicircular truncated conical mandrels 9, 10 is provided on lower surfaces of the pair of jaws 7, 8 (see FIG. 8).
As shown in FIG. 8, the pair of mandrels 9, 10 is constructed such that, when the jaws 7, 8 are closed, the two semicircular truncated conical mandrels 9, 10 abut mutually with each other to form a circular truncated cone.
Thus, when the pipe expanding tool 1 is used to expand an end of a tube 11, as shown in FIG. 9, first, in a state in which the jaws 7, 8 are closed, the circular truncated cone formed by the mandrels 9, 10 is inserted into an open end of the tube 11. Next, when the grips 5, 6 are displaced in directions to approach one another, as shown in FIG. 10, the levers 3, 4 are rotated about the rotary shaft 2, and the jaws 7, 8 are expanded. Accompanying expansion of the jaws 7, 8, the mandrels 9, 10 separate away from each other, and the circumferential side surfaces of the mandrels 9, 10 are pressed outwardly against the inner circumferential surface of the end of the tube 11, whereby the end of the tube 11 is expanded.
Furthermore, when the grips 5, 6 are displaced in directions to approach one another, the levers 3, 4 rotate further, and inside end surfaces 12, 13 of the levers 3, 4 abut mutually against each other. Rotational movement of the levers 3, 4 is restricted by the inside end surfaces 12, 13, and rotation thereof is stopped. The expanding motion of the jaws 7, 8 is brought to an end accompanying the stop in rotation of the levers 3, 4. At this time, the circumferential side surfaces of the mandrels 9, 10, which have pressed the end of the tube 11 outwardly from the inner side thereof, arrive at displacement end positions, whereupon the pipe expanding operation with respect to the end of the tube 11 is completed. Thus, by utilizing the pipe expanding tool 1 in the above sequence of steps, the end of the tube can be expanded.